Senior Backend Developer

Type: Contract (3 months) Location: Remote Experience: 5+ years Compensation: $5,000 USD Stack: TypeScript · NestJS · PostgreSQL · Google Cloud About the role We're building the backend for a social activity-sharing platform where users coordinate availability with friends, plan hangouts, chat, and discover activities. The mobile frontend (web + iOS/Android) is already built and expects a REST API with JWT auth and a refresh-token flow. We're looking for a senior engineer to own the backend end-to-end — architecture, build, and production launch. This is a high-ownership role: you'll make the foundational technical decisions, set up the infrastructure, and ship a scalable system that a growing product will rely on. You should be comfortable working autonomously and setting the standard others build on. What you'll own - Architecture & core API — Design and build a scalable REST API in NestJS (TypeScript) (Controller → Service → Repository), with auto-generated OpenAPI docs to keep the client in sync. You own the architecture decisions. - Database — Design the PostgreSQL schema for the social domain (users, friends, hangouts, activities, interests, notifications); own migrations, indexing, and query performance. Add Redis for caching, rate-limiting, and sessions. - Authentication — Implement self-issued JWT access/refresh tokens (rotation + revocation) plus Google and Apple OAuth, integrating cleanly with the existing client's 401→refresh→retry flow. - Chat engine — Build a scalable real-time chat/messaging system (1:1 + group) — WebSockets, persistence, delivery/read receipts, presence, and Redis pub/sub for multi-instance scaling. Evaluate build-vs-buy (e.g., Stream/Ably) and make the call. - Storage on Google Cloud — Set up Google Cloud Storage for user media with signed URLs, upload validation, and access control. - Payments — Integrate payments (Stripe and/or mobile IAP via RevenueCat) — checkout, subscriptions, webhooks, and secure key handling. - Notifications & jobs — FCM push notifications and background jobs (BullMQ) for fan-out, digests, and async work. - Infrastructure & delivery — Containerize (Docker), deploy to Google Cloud (Cloud Run / GKE), and own CI/CD, secrets, observability (logging/metrics/alerting), and cost. What we expect from a senior hire - 5+ years building and shipping production backend systems, with real ownership of services at scale - Track record of designing systems from scratch and making sound architecture/build-vs-buy trade-offs - Experience scaling APIs and databases (performance tuning, caching strategy, horizontal scaling) - Ability to work autonomously, set technical direction, and mentor / set standards for future team members - Strong on security and reliability — auth, data protection, PCI-aware payment handling, incident readiness Required skills - Expert TypeScript + Node.js; production NestJS (or strong Express/Fastify + willingness to adopt NestJS) - PostgreSQL schema design, migrations, and query optimization (Drizzle/Prisma); Redis - Authentication — JWT, OAuth 2.0 (Google/Apple), secure token lifecycle - Real-time systems — WebSockets, pub/sub, presence, messaging at scale - Google Cloud — Cloud Storage, Cloud Run/GKE, IAM, Secret Manager - Payments — Stripe or mobile IAP, webhooks, PCI-aware practices - REST API design, OpenAPI/Swagger, Docker, CI/CD, monitoring Nice to have - Integrating with mobile clients (Flutter/Dio) · FCM push - PostGIS/geospatial (location-based features) - LLM API integration (Gemini/OpenAI) -Prior social or messaging apps at scale; leading/mentoring engineers Compensation Total: $5,000 USD — fixed-term, 3-month contract $1,500 / month for 3 months ($4,500), paid at the end of each month $500 completion bonus released on successful delivery and acceptance of all milestones Deliverables - A deployed, documented, production-ready backend with a live API URL and CI/CD - Postgres schema + migrations matching the existing frontend data models - Working auth (email/password + Google + Apple), chat, GCS storage, and payments - OpenAPI spec + generated client, plus a README/runbook for local setup and deployment